PLAN: The proposed research will study children at high risk of hypertension because of hypertensive parents. Since blood pressure rises with age have been shown to begin during the childhood, this period may be ideal to study the genesis of hypertension. Changes of Physical (blood pressure) and Humoral (urinary kallikrein, prostaglandins, catecholamines and plasma renin) factors in response to exercise will be measured. A prospective four year study is planned in the form of a re-examination of both physical and humoral factors two years following the initial measurements. PREVIOUS WORK: Results from preliminary studies at the Medical University have suggested the hypothesis that exercise stress testing of children may provide clues to identify risk factors, if not precursors, of adult hypertension because (1) such stress testing has shown a group of hyper-reactors in that their blood pressure responses were above the upper extreme of the distribution of "normal" children. (2) Certain humoral factors, measured in Medical University of South Carolina research laboratories, seem to correlate with this finding. POPULATION: Prospective study participants are available from those registered in the computer of the Family Practice Department at the Medical University of South Carolina. The population of this registry is shown to be similar to the population of Charleston County, South Carolina (an area with a high incidence of hypertension) as regards age, race, sex and income characteristics. ANALYSIS: Case-control approaches are proposed to test the study hypothesis by estimating the odds of an effect, given selected characteristics such as vasoconstrictors (renin; catecholamines), vasodilators (prostaglandins; killikreins), obesity, cardiac output and family history. Control of confounding and interactive effects are planned in both categorical and continuous analyses. Further long-term prospective studies might be planned if "tracking" seems apparent at the two year repeat evaluation.